His former flame has accused the Nickelback rocker of cheating on her with the Complicated singer.

Kristen, 27, has also taken to Twitter in a bid to articulate her shock, saying: 'the moment u find out ur ex of four months engaged the girl he was cheating on you with! #classic.'

However, she then wrote: 'Thx for the sweet comments! Sometimes 140 characters is just not enough for what I would like to say! #whatgoesaroundcomesaround. Learned a lesson. Moved on.'

Did he or didn't he? Kristen DeWitt, the ex-girlfriend of Nickelback star Chad Kroeger, is claiming he cheated on her with singer Avril Lavigne - as they split in May, but Chad and Avril reportedly started dating in February

Tainted love: Kristen had reportedly been dating Chad for several years

In a further attempt to express she is moving on, she retweeted a message that read: 'Got played. Got hurt. Cried Tears. Cursed his name. Learned a lesson. Moved on.'

On Wednesday, it was revealed that 37-year-old Chad had popped the question to Avril after just six months of dating, having initially joined forces to write a song for her upcoming fifth album.

According to RadarOnline, 27-year-old Kristen (the same age as Avril) had been dating Chad for several years following his breakup from long-time Canadian girlfriend Marianne Goriuk in 2002.

A source said: 'Chad and Kristen were happily dating until they made a mutual split in May.

Blushing bride: In an interview with Hello! Canada magazine, Avril says she fell for Chad's sense of humour

'His engagement to Avril completely caught Kristen off guard and the timelines don't match up. Chad had to have been seeing Avril behind Kristen's back.'

Back in April, Chad confirmed to Dave & Jimmy from WNCI radio: 'Yes I'm dating a girl from Ohio.'

According to reports, Avril and Chad have been dating for six months, which mean they began dating in February - yet he and Kristen didn't break up until May.

Canadian Chad, who got down on a bended knee with a 14-carat diamond ring to propose, has posed witho Avril on the front cover of Hello! Canada magazine while showing off the bling.

During the interview with the publication, Avril says she fell for Chad's sense of humour, revealing: 'He makes me laugh every day. He takes care of me in every way and is extremely attentive.'

Working together: The couple were spotted in Paris together in May following work on Avril's fifth album

Chad says he fell for Avril while they were in the studio together working on her record: 'I knew I was falling for her. It was incredibly powerful and something I'll never forget.'

Sources close to Avril and Chad say they are a perfect match because they have the same beliefs.

One told People: 'They have the same values and really understand each other. They complement each other and are so happy. They haven't set a date yet. They're really enjoying this moment.'

Unfortunately for Avril's ex Brody Jenner, the shock announcement fell on his 29th birthday - despite the actual proposal reportedly taking place on August 8.

The couple also confirmed the news on Twitter this week, with Nickelback initially penning a message, saying: 'Congratulations Avril and Chad! Get all the details from @PeopleMag'.

Avril then retweeted the message to her six million followers online.

A source told People: 'He makes her so happy. Both of their families could not be more excited.'